One method to control valve timing of an internal combustion having a variable event valvetrain is described in U.S. Pat. No. 6,681,741. This patent describes several valve timing methods that may be used during starting of an engine having a variable event valvetrain. In particular, the different methods attempt to improve cylinder turbulence and reduce fuel adherence to the intake port. The intake valves are initially set to open at a location that is before top-dead-center of the intake stroke of the cylinder in which the valve operates. After the engine speed reaches a predetermined level the intake valve opening time is switched to position that is after top-dead-center of the intake stroke of the cylinder. The intake valve opening remains at this location until a change in an operating condition causes the intake valve opening time to return to a position before top-dead-center of the intake stroke.
The above-mentioned method can also have several disadvantages. Specifically, the cylinder air-fuel mixture may not mix as well as desired when the engine is being cranked or when it is accelerating from crank speed up to the time it reaches a certain operating speed (run-up). Further, engine fuel consumption may be higher than desired because the cylinder charge motion and air-fuel mixing may not be sufficient at low engine speed to improve combustion. In other words, portions of the cylinder air-fuel mixture may combust less completely than other portions of the cylinder air-fuel mixture due to lack of homogeneity of the air-fuel mixture. Further still, the method only appears to recognize that it is desirable to heat an exhaust after treatment device. The method does not appear to recognize that there are additional benefits that can be achieved by quickly heating the engine and engine fluids.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method of controlling intake manifold pressure that offers substantial improvements.